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diff --git a/notefreq b/notefreq
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+#!/usr/bin/perl -w
+
+sub usage {
+	die <<EOF;
+Usage: $0 [-annn] note
+
+Where `note' is a letter A through F, with optional # or b (sharp
+or flat), followed by an octave number (e.g. A4 is a concert A, E1 is
+the low E on a bass, E2 is the low E on a guitar, C4 is "middle C").
+
+Frequencies are by default calculated using "concert pitch", where A4 = 440Hz.
+If -annn option is given, the "nnn" will be used as the pitch of A4 instead.
+(In other words, "-a440" is the default).
+
+EOF
+}
+
+%notes = (
+		C => 1,
+		'C#' => 2,
+		Db => 2,
+		D => 3,
+		'D#' => 4,
+		Eb => 4,
+		E => 5,
+		F => 6,
+		'F#' => 7,
+		Gb => 7,
+		G => 8,
+		'G#' => 9,
+		Ab => 9,
+		A => 10,
+		'A#' => 11,
+		Bb => 11,
+		B => 12
+		);
+
+if(@ARGV && ($ARGV[0] =~ /^-a([.\d]+)$/)) {
+	$ref = $1;
+	shift;
+} else {
+	$ref = 440; # A440
+}
+
+$refnum = $notes{A} + 12*4;
+
+$_ = shift;
+($note, $oct) = /^([A-G][#b]?)-?(\d\d?)/i;
+
+usage unless $note;
+
+$num = $notes{ucfirst lc $note} + (12*$oct) - $refnum;
+
+$freq = $ref * (2 ** ($num/12));
+
+print "$freq\n";